Subtitles section Play video Print subtitles [MUSIC] [MUSIC] [MUSIC] Psychologist Endel Tulving said, “Remembering is mental time travel”. Soy Latte for Joe… Thanks. Remembering is one of the greatest powers we possess… [SNEEZE] the ability to learn from our past, to return to where we have already been, so we can decide where we're going. "Oh man…" But can we return to where we’ve… never been? Soy Latte for Joe… Yeah… huh thanks? Could have sworn I just- [SNEEZE] Is it just me, or does this seem familiar? Feel I’ve seen this before. "Oh man…" Or as the French would say… déjà vu… As many as 90 percent of us will experience déjà vu during our lives, mainly in our teens and 20s, and almost never before age 8 or 9. Déjà vu isn’t a physical phenomenon we can pinpoint in a brain scan. It’s a feeling, and not one that we totally understand. But we’ve got a few theories. Our memories aren’t exact copies that we just write once and then store like files on a computer, or pictures in a box under our bed. Remembering is really more like reliving. Our brains are constantly scanning our senses to determine if what we’re experiencing is familiar. And once our brains label a stimulus as familiar, a different brain region called the hippocampus recalls the memory associated with it, re-firing the neural circuits that hold that piece of our past, and we live the experience again in our minds. If these steps get out of sync, if something is deemed familiar, but we fail to recall the context, that could be déjà vu. But that doesn’t explain why we can feel déjà vu for experiences that are truly unfamiliar, or why we don’t feel it for every familiar thing. Soy Latte for Joe… Yep. We don’t realize how hard our brain works behind the scenes, filtering our environment— [SNEEZE] —Gesundheit!— unconsciously determining if what we’re experiencing is new…until it doesn’t work. Oh! "Oh man…" Our various sensory inputs… smells, sounds, sights, are normally processed and mixed together as one event. Another déjà vu theory says if one of those stimuli is recorded out of sync, the late arriving information could be flagged as a different event, which makes it feel as if it’s happened before. Or it could be a malfunction in how memories are made in the first place. Normally, new experiences stop off in our short term memory before being written into long-term storage. Skip the first, and it could feel like we’re recalling new events as old ones. Or perhaps when we focus on one part of our environment, the rest of our world drifts to the unconscious, and when we snap back to reality it feels like we’ve been there before… because we have. Just now. These feelings of misplaced familiarity, are… familiar to us, but the what, the where, and the why of déjà vu remain unknown. Soy Latte for— Got it thanks. All in all, there are dozens of plausible explanations for it, maybe more than one is right. Bless you! There’s no neat answer, but no mind, or memory, is perfect. The only way we’ll get to the bottom of déjà vu is to experience it… all over again. "Oh man…" Yeah, I could’ve. Stay curious.